1. Field of the Invention
This invention relates to an electric connection box such as a junction box.
2. Description of the Related Art
One example of known junction boxes comprises a body having electrical parts (such as relays and fuses) mounted thereon, and a cover attached to a lower surface of the body. A wire harness is extended outwardly from a predetermined portion of the body. A plurality of elastically-deformable lock piece portions are formed on and project from the body, and lock portions, corresponding respectively to the lock piece portions, are formed at the cover. The lock piece portions are elastically deformed to be retainingly engaged with the lock portions respectively, thereby connecting the cover to the lower surface of the body in a united manner. This cover is fixedly secured to a vehicle body by screws.
This kind of junction box is disclosed, for example, in JP-A-2001-218335.
When disassembling a vehicle, such a junction box is removed from a vehicle body for assorting recovery purposes or other purposes. At this time, for the purpose of saving the time and for other purposes, the whole of the box is not removed by loosening the screws, but only the body is withdrawn from the cover by gripping and pulling the wire harness, with the cover remaining on the vehicle body. On the other hand, when the junction box is in use, a predetermined force of connection between the cover and the body is required, and therefore lock mechanisms are provided respectively at a plurality of portions to increase the connecting force, and therefore when withdrawing the body from the cover as described above, this operation can not be effected easily, causing a problem that much time and labor are required for the disassembling operation.
An object of the invention is to provide a connecting structure which provides a high retaining force and facilitates a disassembling operation.
According to a first aspect of the invention, there is provided an electric connection box comprising: a connection box body having electrical parts such as a relay and a fuse mounted thereon; a wire harness being extended outwardly from a predetermined portion of the connection box body; a cover attached to one surface of the connection box body; and a plurality of lock mechanisms being disposed respectively at regions between the connection box body and the cover, wherein one of the lock mechanisms, disposed near to a position where the wire harness is extended outwardly, has a smaller retaining force than that of the other lock mechanisms.
According to a second aspect of the invention, each of the lock mechanisms includes an elastically-deformable lock piece portion provided at one of the connection box body and the cover, and a lock portion provided at the other so as to be retainingly engaged with the lock piece portion, and in the lock mechanism having the smaller retaining force, at least one of mating surfaces of the lock piece portion and the lock portion, which can be retainingly engaged with each other, is tapering to provide a semi-lock structure.
According to a third aspect of the invention, each of the lock mechanisms includes an elastically-deformable lock piece portion provided at one of the connection box body and the cover, and a lock portion provided at the other so as to be retainingly engaged with the lock piece portion, and in the lock mechanism having the smaller retaining force, the lock piece portion is disposed in such a posture that the lock piece portion can be easily broken at a proximal end portion thereof when a force, acting to separate the lock piece portion from the lock portion, is applied to the lock piece portion.
According to the first aspect, the cover is fixedly secured to a fixing member, and in this condition when the wire harness is gripped and pulled in a predetermined direction, the lock mechanism, which is disposed near to the position where the wire harness is extended outwardly and has the relatively-small retaining force, is unlocked, and part of the body is withdrawn from the cover, and subsequently the other lock mechanisms, while subjected to an inertia force of this withdrawing operation, are unlocked in a chain-like manner, and the body is withdrawn from the cover.
Only that lock mechanism, disposed near to the position where the wire harness is extended outwardly, has the smaller retaining force, and the required overall retaining force is secured, and the withdrawal of the body can be effected relatively easily.
According to the second aspect, the lock mechanism, disposed near to the position where the wire harness is extended outwardly, has the semi-lock structure, and therefore this lock mechanism can be relatively easily unlocked when the wire harness is pulled.
According to the third aspect, in the lock mechanism, disposed near to the position where the wire harness is extended outwardly, the lock piece portion is broken at its proximal end portion when the wire harness is pulled, so that the locked condition is canceled.